The present invention relates to a flow control device of a helically-shaped intake port of an internal combustion engine.
A helically-shaped intake port normally comprises a helical portion formed around the intake valve of an engine, and a substantially straight inlet passage portion tangentially connected to the helical portion. However, if such a helically-shaped intake port is so formed that a strong swirl motion is created in the combustion chamber of an engine when the engine is operating at a low speed under a light load, that is, when the amount of air fed into the cylinder of the engine is small, since air flowing within the helically-shaped intake port is subjected to a great flow resistance, a problem occurs in that the volumetric efficiency is reduced when the engine is operating at a high speed under a heavy load, that is, when the amount of air fed into the cylinder of the engine is large.
An object of the present invention is to provide a helically-shaped intake port capable of creating a strong swirl motion in the combustion chamber when the amount of air fed into the cylinder is small, while preventing the volumetric efficiency from being reduced when the engine is operating at a high speed under a heavy load.
According to the present invention, there is provided a device for controlling the flow in a helically-shaped intake port of an internal combustion engine, said intake port comprising a helical portion formed around an intake valve, and a substantially straight inlet passage portion tangentially connected to the helical portion and having a helix terminating portion, said device comprising: a bypass passage branched off from the inlet passage portion and connected to the helix terminating portion of the helical portion; a normally closed rotary valve arranged in said bypass passage for controlling the flow area of said bypass passage, and; actuating means for actuating said rotary valve in response to the change in the amount of air fed into the intake port to open said rotary valve when said amount of air is increased beyond a predetermined value.